feat: add guarded Base Sepolia encore

tools/select-manifest.mjs

@@ -1,4 +1,4 @@
-import { readFile } from "node:fs/promises";
+import { access, readFile, rename } from "node:fs/promises";
 import { join, resolve } from "node:path";
 import { pathToFileURL } from "node:url";
 
@@ -14,9 +14,33 @@ export async function selectManifest({ root = process.cwd(), network }) {
   return { source, active };
 }
 
+export async function archiveManifest({ root = process.cwd(), network, now = new Date() }) {
+  if (network !== "baseSepolia") throw new Error("only baseSepolia may be archived");
+  const spec = networkSpec(network);
+  const source = join(root, "deployments", spec.canonical);
+  await readManifest(source);
+  if (!(now instanceof Date) || Number.isNaN(now.valueOf())) throw new Error("archive timestamp is invalid");
+  const timestamp = now.toISOString().replace(/[-:.]/g, "");
+  if (!/^\d{8}T\d{9}Z$/.test(timestamp)) throw new Error("archive timestamp is invalid");
+  const target = join(root, "deployments", `base-sepolia.${timestamp}.json`);
+  try {
+    await access(target);
+  } catch (error) {
+    if (error.code === "ENOENT") {
+      await rename(source, target);
+      return { source, path: target };
+    }
+    throw error;
+  }
+  throw new Error("refusing to overwrite an existing Base Sepolia archive");
+}
+
 export async function runSelectCli(argv, { root = process.cwd(), log = console.log } = {}) {
   log(EDUCATIONAL_WARNING);
-  if (argv.length !== 1) throw new Error("usage: select-manifest.mjs <anvil|baseSepolia>");
+  if (argv.length === 2 && argv[0] === "archive" && argv[1] === "baseSepolia") {
+    return archiveManifest({ root, network: argv[1] });
+  }
+  if (argv.length !== 1) throw new Error("usage: select-manifest.mjs <anvil|baseSepolia> | archive baseSepolia");
   return selectManifest({ root, network: argv[0] });
 }